Polymer composition including functional material, method for production of the same, inkjet ink, and image formation method and image formation apparatus using the same

ABSTRACT

A polymer composition including a functional material, the composition containing at least a block polymer encapsulating a material of a predetermined function and a solvent, wherein a property of the polymer in the composition is changed in response to a stimulus, whereby the block polymer encapsulating the material agglomerates together, or an ink composition usable as an inkjet ink containing at least a block polymer encapsulating a coloring material and a solvent, wherein a property of the polymer in the composition is changed in response to a stimulus, whereby the block polymer encapsulating the coloring material agglomerates together. The change of the property of the block polymer in response to a stimulus is a change from the lyophilic nature to the lyophobic nature, or the lyophilic nature to the lyophobic nature.

TECHNICAL FIELD

The present invention relates to a composition containing a blockpolymer encapsulating a material of a predetermined function and asolvent, a method for production of the same, and an image formationmethod and an image formation apparatus using the composition.

BACKGROUND ART

Aqueous dispersions containing functional materials have been widelyused for agricultural chemicals such as herbicides and insecticides anddrugs such as anticancer drugs, antiallergic drugs and anti-inflammatorydrugs as functional materials. Meanwhile, coloring materials such as inkand toner containing a colorant in a form of solid particles are wellknown. In recent years, digital printing technologies represented byelectrophotography and inkjet printing have been making great progress,and the significance of these technologies as an image formationtechnology is recognized more and more in office and home.

Among them, the inkjet technology has remarkable features such ascompactness and low power consumption as a direct recording method. Inaddition, image quality has been rapidly improved owing to refinement ofnozzles and the like. One example of the inkjet technology is a methodin which ink supplied from an ink tank is heated by a heater in a nozzleto form a bubble therein by boiling, and the ink is discharged from thenozzle to form an image on a recording medium. Another method is amethod in which a piezo element is vibrated to discharge ink from anozzle. Since an aqueous dye solution is usually used in ink used inthese methods, bleeding may occur when colors are superimposed, and aphenomenon called feathering may occur along paper fibers at a recordinglocation on the recording medium. For the purpose of alleviating theseproblems, use of pigment dispersion ink is proposed (U.S. Pat. No.5,085,698). However, many improvements are still desired.

DISCLOSURE OF THE INVENTION

In view of the above situations, the present invention provides acomposition characterized in that a block polymer encapsulating afunctional material agglomerates together in response to a stimulusapplied.

Particularly, the present invention provides a composition suitable foran inkjet ink that alleviates bleeding and feathering and is excellentin fixation.

The present invention provides an image formation method and an imageformation apparatus using the composition described above.

The first aspect of the present invention relates to a compositioncomprising a block polymer encapsulating a functional material of apredetermined function and a solvent, wherein the property of the blockpolymer changes in response to the applied stimulus, whereby the blockpolymer encapsulating the functional material agglomerates together.

The second aspect of the present invention is a method for production ofthe composition that agglomerates together in response to a stimulus,the method comprises the steps of:

completely dissolving a block polymer in a solvent; and

encapsulating the functional material in the block polymer by a changein the solvent environment.

The third aspect of the present invention is an image formation methodcharacterized in that an image is formed on the medium through a processthat the composition is applied to a medium, and the property of theblock polymer is changed in response to a received stimulus, whereby theblock polymer encapsulating the functional material agglomeratestogether. The block polymer preferably forms micelles. Particularly, ina polymer-containing composition containing a material having afunctional material included in an amphipathic block polymer having ahydrophobic segment and a nonionic hydrophilic segment and a solvent, itis preferable that the particle size of the material is increased by achange in pH for fixation on a recording medium.

The fourth aspect of the present invention is an image formationapparatus that comprises means for applying the composition to a medium,and is used for forming an image on the medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an outlined mechanism of an image recording apparatus ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail below.

The inventors of the present invention studied the above-describedsituations and technical problems and completed the present invention.

The first aspect of the present invention is a composition comprising ablock polymer encapsulating a functional material of a predeterminedfunction and a solvent, characterized in that a property of the blockpolymer will change in response to a stimulus applied, whereby the blockpolymer encapsulating the functional material agglomerates together.Hereinafter such a composition is referred to as “the composition”.Preferably, such a composition contains micelles of a block polymerencapsulating a functional material of a predetermined function and asolvent, characterized in that a property of the block polymer willchange in response to a stimulus applied to cause aggregation of theblock polymer micelles.

The “material being encapsulated in a block polymer” refers to such astate that a material is enclosed in the block polymer, e.g., a coloringmaterial exists in hydrophobic core portions of the micelles of theblock polymer in water.

The solvent (liquid medium) contained in the composition of the presentinvention is not specifically limited as long as it can dissolve,suspend or disperse the components of the composition. In the presentinvention, the solvent includes organic solvents such as various kindsof straight, branched or cyclic aliphatic hydrocarbons, aromatichydrocarbons and heteroaromatic hydrocarbons, aqueous solvents andwater. In order to accelerate drying on a recording medium such aspaper, monohydric alcohols such as methanol, ethanol and isopropylalcohol may be used.

The second aspect of the present invention is a method for production ofthe composition characterized in that the polymer is completelydissolved in a solvent, and then the solvent environment is changed tomake the material included in the block polymer. More preferably, thechange in solvent environment in the production method is at least oneselected from change in temperature, irradiation with an electromagneticwave, change in pH of the composition and change in the concentration ofthe composition. The range of temperature change preferably includes thephase transition temperature of the composition. Regarding the exposureto electromagnetic waves, the wavelength of the electromagnetic wave ispreferably in the range of 100 to 800 nm. The range of pH change ispreferably from pH 3 to pH 12. The range of the concentration changepreferably covers a concentration at which the composition undergoesphase transition.

The third aspect of the present invention is an image formation methodfor forming an image by applying ink onto a recording medium,characterized in that a dispersion composition containing a blockpolymer encapsulating a coloring material is used as ink and a propertyof the polymer will change in response to a stimulus to causeagglomeration of the block polymer molecules. Preferably, the imageformation method is characterized in that the dispersion compositioncontains a block polymer that forms micelles to encapsulate the coloringmaterial and an image is formed through a process in which a property ofthe polymer changes in response to a stimulus applied to causeaggregation of the micelles of the polymer. More preferably, thestimulus applied in the image formation method is at least one selectedfrom temperature change, irradiation of electromagnetic wave, pH changeand change in concentration of the composition. The range of temperaturechange preferably includes the phase transition temperature of thecomposition. Regarding the exposure to electromagnetic waves, thewavelength of the electromagnetic wave is preferably in the range of 100to 800 nm. The range of pH change is preferably from pH 3 to pH 12. Therange of the concentration change preferably covers a concentration atwhich the composition undergoes phase transition.

The fourth aspect of the present invention is an image formationapparatus to be used for image formation using a dispersion compositionthat contains a block polymer encapsulating a pigment through a processin which a property of the polymer changes in response to a stimulusapplied to cause agglomeration of the pigment-encapsulating blockpolymer. Preferably, it is an image formation apparatus to be used forimage formation using a dispersion composition that contains blockpolymer micelles encapsulating a pigment through a process in which aproperty of the polymer changes in response to a stimulus applied tocause agglomeration of the micelles of the block polymer. Morepreferably, the stimulus applied in the image formation method is atleast one selected from temperature change, irradiation ofelectromagnetic wave, pH change and change in concentration of thecomposition. The range of temperature change preferably includes thephase transition temperature of the composition. Regarding the exposureto electromagnetic waves, the wavelength of the electromagnetic wave ispreferably in the range of 100 to 800 nm. The range of pH change ispreferably from pH 3 to pH 12. The range of the concentration changepreferably covers a concentration at which the composition undergoesphase transition.

The block polymer for use in the present invention is preferably anamphipathic block polymer. It is preferably an amphipathic block polymerhaving a hydrophobic segment and a nonionic hydrophilic segment, inother words, the block polymer contains at least one hydrophobic segmentand at least one nonionic hydrophilic segment. Types of block structuresinclude the followings. Representative ones are block polymers of ABtype having different block segments, tri-block polymers of ABA havingthe same block segments at both ends, and tri-block polymers of ABC typehaving different block segments. There are also block polymers of ABCDtype having different block segments, block polymers of ABCA type andblock polymers having a larger number of block segments.

In the case of tri-block polymers of ABC type or block polymers havingthree or more block segments, at least one hydrophobic segment and atleast one nonionic hydrophilic segment should be included in the blocksegments, and the other block segment may be a block segment having anionic functional group.

The block polymers described above can be previously known blockpolymers such as acrylate or methacrylate block polymers, block polymersof polystyrene and other polymers of addition polymerization orcondensation polymerization, and block polymers of polyoxyethylene andpolyoxyalkylene.

More preferable one is a block polymer having a polyalkenyl etherstructure as a repeating unit structure, and further more preferable oneis a compound having a polyvinyl ether structure as a repeating unitstructure.

Each block segment of the block polymer compound of the presentinvention may be composed of a single type of repeating units or may becomposed of two or more types of repeating units. Examples of blocksegments composed of two or more types of repeating units include randomcopolymers and graduation copolymers having composition ratios graduallychanged. The block polymer compound of the present invention may be apolymer where a block polymer of three or more block segments is bondedto another polymer by grafting.

The number average molecular weight (Mn) of the block polymer compoundof the present invention is 200 to 10,000,000, preferably 1,000 to1,000,000. If the number average molecular weight is greater than10,000,000, entanglement within a polymer chain and between polymerchains may become so severe that the polymer is hard to be dispersed ina solvent. If the number average molecular weight is less than 200, themolecular weight is so small that a steric effect of the polymer may notbe obtained. The polymerization degree of each block segment ispreferably from 3 to 10,000. More preferable is from 5 to 5,000. Furthermore preferable is from 10 to 4,000.

For improvement of dispersion stability and improvement of inclusionproperties (encapsulating properties), it is preferable that moleculesof the block polymer are more flexible because the polymer canphysically entangle with the surface of the functional material toincrease affinity. As described in detail later, the flexibility ispreferable in the point that a covering layer is easily formed on arecording medium. For this purpose, the glass transition temperature Tgof the main chain of the block polymer is preferably 20° C. or lower,more preferably 0° C. or lower, further more preferably −20° C. orlower. In this respect, a polymer having a polyvinyl ether structure ispreferably used because the polymer generally has a low glass transitiontemperature and has flexible properties. Most of the example repeatingunit structures described above have a glass transition temperature ofabout −20° C. or lower.

Polyvinyl ether that is characteristically used in the present inventionis described. The features of the composition of the present invention,that is high dispersion stability, alleviation of bleeding andfeathering and excellence in fixation, are mostly due to the polymermaterial having a polyvinyl ether structure used in the dispersion. Asdescribed above, stimulus responsivity in the present invention meansthat the shape or physical properties change drastically in response toenvironmental stimuli such as exposure to an electromagnetic wave,application of an electric field, temperature change, pH change,addition of a chemical material or concentration change of thecomposition. A polymer having a polyvinyl ether structure can providestimulus responsibility to the composition. In such a composition, it ispreferable the polymer also serves as a stabilizer of a pigmentdispersion. Thus, polyvinyl ether preferably has both hydrophilic andhydrophobic portions, i.e. an amphipathic structure. Specifically, apolymer obtained by copolymerization of a hydrophilic monomer and ahydrophobic monomer can be a preferred example. Such a polymer having apolyvinyl ether structure has more preferable dispersion propertiesbecause the polyvinyl ether structure generally has a low transitiontemperature and flexibility, and its hydrophobic portion tends tophysically entangle or has affinity with solid particles.

Various methods for synthesis of a polymer having a polyvinyl etherstructure have been reported (for example, Japanese Patent ApplicationLaid-Open No. H11-080221), among which a method by cationic livingpolymerization by Aoshima et al. (Japanese Patent Application Laid-OpenNos. H11-322942 and H11-322866) is representative. By synthesizingpolymers by cationic living polymerization, various polymers such ashomopolymers, copolymers of 2 or more monomers and block polymers, graftpolymers and graduation polymers can be synthesized with the same length(molecular weight). Polyvinyl ether can have various functional groupson the side chain. Cationic polymerization can be carried out by theHI/I₂ system, HCl/SnCl₄ system or the like.

The first object of the addition of a polymer having a polyvinyl etherstructure in the present invention is to provide stimulus responsivity,but other functions such as dispersion of solid particles (pigment etc.)may be also provided.

Typical stimuli and polymers of a polyvinyl structure responsive to thestimuli will be illustrated below.

Responses of the composition to changes in temperature include changesin solubility, thermal polymerization, changes in polarity, phasetransition (sol-gel transition, liquid crystals) and the like. The rangeof the temperature change preferably covers the phase transitiontemperature of the composition, and more preferably covers a criticalgel temperature. Polyvinyl ether structures responsive to a temperaturestimulus are, for example, alkoxy vinyl ether derivatives such aspoly(2-methoxyethyl vinyl ether) and poly(2-ethoxyethyl vinyl ether),and copolymers having these polymer compounds as the main components.Particularly, a block polymer of poly((2-methoxyethyl vinylether)-b-(2-ethoxyethyl vinyl ether)) causes a rapid change in viscosityat 20° C. Here b indicates being a block polymer.

Next stimulus responsivity is responsivity to exposure to anelectromagnetic wave. The wavelength of the electromagnetic wave is morepreferably in the range of 100 to 800 nm. Responses to a stimulus ofexposure to an electromagnetic wave include, for example, solubilitychange, photo-polymerization, photochromism, photoisomerization,photodimerization, phase transition (sol-gel transition, liquidcrystals). Polyvinyl ether structures responsive to the stimulus mayinclude, for example, vinyl ether derivatives having functional groupsfor polymerization, such as poly(2-vinyloxyethyl methacrylate) andcopolymers having such a polymer compound as the main component.

Regarding the response to a stimulus of pH change, it is preferable forthe composition to respond to changes in the range of pH 3 to 12.Responses to a stimulus of pH change may include, for example, changesin solubility, hydrogen bonding and coordination bonding and polarityand phase transition (sol-gel transition, liquid crystals). Structuresof the polymers having a polyvinyl ether structure, to be contained in adispersion responsive to the stimuli, may include, for example,copolymers and polymer blends of alkoxy vinyl ether derivatives such aspoly(2-methoxyethyl vinyl ether) and poly(2-ethoxyethyl vinyl ether) andpolycarboxylic acid such as polymethacrylic acid.

Further stimulus examples may include concentration change in an aqueousink. The stimulus is given by, for example, vaporization or absorptionof water of the aqueous ink or a change in concentration of a polymerdissolved in the composition. For the stimulus, the concentration changepreferably covers the phase transition concentration of the composition,and more preferably it covers a critical gel concentration. Response ofthe composition to the stimulus of concentration change includes, forexample, hydrogen bonding, hydrophobic interaction and phase transition(sol-gel transition, liquid crystals). One example polymer is an alkoxyvinyl ether derivative such as poly(2-methoxyethyl vinyl ether) orpoly(2-ethoxyethyl vinyl ether) or the like, aryl oxyvinyl etherderivative such as poly(2-phenoxyethyl vinyl ether) or copolymer havingsuch a polymer as the main component.

Of these stimuli, two or more of types of stimuli can be combined. Thefunction of stimulus response can be provided by a polymer having apolyvinyl ether structure. In the present invention, other polymers canbe used to improve the function. For example, a polymer not having apolyvinyl ether structure can be used to provide stimulus responsivity,and a polymer having a polyvinyl ether structure is used to provideother functions (e.g. dispersion stability). Examples of other polymershaving stimulus responsivity include those described below, but thepresent invention is not limited thereto. By adding into the compositiona polymer other than a polymer having a polyvinyl ether structure (e.g.polymer having stimulus responsivity described above), stimulusresponsivity can be added or improved.

A first example is such a polymer that causes phase transition when thecomposition is heated to cause change in the composition. Specificexamples of such a polymer include poly(meta)acrylamide, poly N-alkylsubstituted(meta)acrylamide such as poly-N-isopropyl(meta)acrylamide,poly N-vinylisobutylamide, poly(meta)acrylic acid or metal saltsthereof, poly-2-hydroxyethyl(meta)acrylate,poly-N-(meta)acrylpiperidine, poly(2-ethyloxazolin), polyvinyl alcoholor partially saponified products thereof, polyethylene oxide, copolymersof polyethylene oxide and polypropylene oxide,poly(ethyleneglycolmonomethacrylate), poly(ethyleneglycolmonoacrylate),substituted cellulose derivatives such as methylcellulose,ethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose andcopolymers and polymer blends having these polymer compounds as the maincomponents.

A second example is such a polymer that undergoes structure change byphotoreaction to cause phase transition when the composition is exposedto the electromagnetic wave, to cause a change in the composition.Specific examples of the polymer include polymer compounds having groupssuch as photochromic groups. Specifically, they include various kinds ofpolymers, for instance, triphenylmethane derivatives that undergoes ioncleavage by light, poly(meta)acrylamides having a spiropyran derivativeor spirooxazine derivative group, poly N-alkyl substituted(meta)acrylamides such as poly-N-isopropyl(meta)acrylamide andN-vinylisobutylamides.

A third example is such a polymer that causes phase transition when thecomposition of the composition is changed by a change in pH. Specificexamples of such a polymer include poly(meta)acrylic acid or metal saltsthereof, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid,poly(meta)acrylamidealkylsulfonic acid, polymaleic acid or metal saltsthereof, or copolymers based on monomer components constituting thesepolymer compounds, polyvinyl alcohol-polyacrylic acid composites ormetal salts thereof, poly(ethyleneglycolmonomethacrylate), metal saltsof carboxymethylcellulose, metal salts of carboxyethylcellulose, andcopolymers and polymer blends having as main components these polymercompounds.

A fourth example is such a polymer that causes phase transition, whenthe concentration of the polymer dissolved in the composition ischanged. Specific examples of such a polymer include polymer compoundshaving a lower critical solution temperature (LCST) such aspoly(meta)acrylamide, poly N-alkyl-substituted(meta)acrylamide,polyvinyl methyl ether and polymethacrylic acid as aqueous solutions(Japanese Patent publication No. S61-7948, Japanese Patent ApplicationLaid-Open No. H3-237426 and Japanese Patent Application Laid-Open No.H8-82809), polyvinyl alcohol, polyvinyl alcohol-polyacrylic acidcomplexes or metal salts thereof, poly(ethyleneglycol monomethacrylate),inorganic polymers such as alkoxy siloxane, and copolymers and polymerblends having as main components these polymer compounds.

The structure of the block polymer in the composition is notspecifically limited but particularly, a polymer having a vinyl etherstructure in at least one of the segments is more preferable.

Block polymer retains respective properties of the repeating monomerunits of the blocks or units, and can exhibit these properties in acoexistent manner. These polymers can more effectively function thanrandom polymers, since block or unit portions having stimulusresponsivity can function effectively. Further, these polymers enabledispersion of solid particles an aqueous medium used to disperse thepolymer. In this case, a part of the polymer should have an affinity forthe aqueous solvent used. In the case of the polymer having a polyvinylether structure, various block forms such as AB, ABA and ABC arepossible as described above, and the polymer preferably has two or moredifferent types of hydrophilic blocks. The polymer can have ionic sitesat its end.

The repeating unit structure of the polymer having the polyvinyl etherstructure is not specifically limited, but preferable is expressed bythe following General Formula (1):

wherein R¹ is selected from the group consisting of a straight, branchedor cyclic alkyl group having 1 to 18 carbon atoms, phenyl(Ph),pyridyl(Pyr), Ph-Ph, Ph-Pyr, —(CH(R²) )—CH(R³)—O)₁—R⁴ and—(CH₂)_(m)—(O)_(n)—R⁴, hydrogen on the aromatic ring may be replacedwith a straight or branched alkyl group having 1 to 4 carbon atoms, andcarbon in the aromatic ring may be replaced with nitrogen. 1 is selectedfrom integers of 1 to 18, m is selected from integers of 1 to 36, and nis 0 or 1. R² and R³ are independently H or CH₃. R⁴ is H, a straight,branched or cyclic alkyl group having 1 to 18 carbon atoms, Ph, Pyr,Ph-Ph, Ph-Pyr, —CHO, —CH₂CHO, —CO—CH═CH₂, —CO—C (CH₃)═CH₂ or CH₂COOR⁵,and if R⁴ is not hydrogen, hydrogen on the carbon atom may be replacedwith a straight or branched alkyl group having 1 to 4 carbon atoms or F,Cl or Br, and carbon in the aromatic ring may be replaced with nitrogen.R⁵ is H or an alkyl group having 1 to 5 carbon atoms.

Preferably, R¹ is selected from the group consisting of a straight,branched or cyclic alkyl group having 1 to 18 carbon atoms,—(CH(R²)—CH(R³)—O)₁—R⁴ and —(CH₂)_(m)—(O)_(n)—R⁴. l and m areindependently selected from integers of 1 to 12, and n is 0 or 1. R² andR³ are independently H or CH₃. R⁴ is H, a straight, branched or cyclicalkyl group having 1 to 6 carbon atoms, Ph, Pyr, Ph-Ph, Ph-Pyr, —CHO,—CH₂CHO, —CO—CH═CH₂, —CO—C(CH₃)═CH₂ or CH₂COOR⁵, and if R⁴ is nothydrogen, hydrogen on the carbon atom may be replaced with a straight orbranched alkyl group having 1 to 4 carbon atoms. F, Cl or Br, and carbonin the aromatic ring may be replaced with nitrogen. R⁵ is H or an alkylgroup having 1 to 5 carbon atoms.

In the present invention, the straight or branched alkyl group ismethyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl,pentyl, n-hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,octadecyl or the like. The cyclic alkyl group is cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl or the like.Substitution of alkyl may be single or plural.

A preferable repeating unit structure of the polymer having a polyvinylether structure is expressed by the following general formula (2):

wherein R⁶ is selected from the group consisting of a straight, branchedor cyclic alkyl group, Ph, Pyr, Ph-Ph, Ph-Pyr, —(CH₂—CH₂—O)₁—R⁷ and—(CH₂)_(m)—(O)_(n)—R⁷, hydrogen on the aromatic ring may be replacedwith a straight or branched alkyl group having carbon atoms 1 to 4, andcarbon in the aromatic ring may be replaced with nitrogen. l is selectedfrom integers of 1 to 18, m is selected from integers of 1 to 36, and nis 0 or 1. R⁷ is comprised of H, a straight, branched or cyclic alkylgroup having 1 to 18 carbon atoms, Ph, Pyr, Ph-Ph, Ph-Pyr, —CHO,—CH₂CHO, —CO—CH═CH₂, —CO—C(CH₃)═CH₂ or CH₂COOR⁸, and if R⁷ is nothydrogen, hydrogen on the carbon atom may be replaced with a straight orbranched alkyl group having 1 to 4 carbon atoms or F, Cl or Br, andcarbon in the aromatic ring may be replaced with nitrogen. R⁸ is H or analkyl group having 1 to 5 carbon atoms.

Preferably, R⁶ is selected from the group consisting of a straight,branched or cyclic alkyl group having 1 to 18 carbon atoms, Ph, Pyr,Ph-Ph, Ph-Pyr, —(CH₂—CH₂—O)₁—R⁷ and —(CH₂)_(m)—(O)_(n)—R⁷, hydrogen onthe aromatic ring may be replaced with a straight or branched alkylgroup having carbon atoms 1 to 4, and carbon in the aromatic ring may bereplaced with nitrogen. l is selected from integers of 1 to 18, m isselected from integers of 1 to 36, and n is 0 or 1. R⁷ is comprised ofH, a straight, branched or cyclic alkyl group having 1 to 18 carbonatoms, Ph, Pyr, Ph-Ph, Ph-Pyr, —CHO, —CO—CH═CH₂ or —CO—C(CH₃)═CH₂, andif R⁷ is not hydrogen, hydrogen on the carbon atom may be replaced witha straight or branched alkyl group having 1 to 4 carbon atoms or F, Clor Br, and carbon in the aromatic ring may be replaced with nitrogen.

More preferably, regarding the repeating unit molecular structure of thepolymer that has the polyvinyl ether structure in the compositiondescribed above, the following vinyl ether monomers can be recited, butnot limited thereto.

Block polymers having a polyvinyl ether structure made from these vinylether monomers can be suitably used in the present invention. Thepolymer that can be used in the present invention is not limited tostimulus-responsive polymers having a polyvinyl ether structure madefrom the vinyl ether monomers described above. Examples of thesepolymers are recited below, but not limited thereto.

Preferably, the numbers of repeating units of polyvinyl ether (x, y andz in (II-a) to (II-g) described above) are independently 1 to 10,000 andmore preferably, the total of the numbers ((x+y+z) in (II-a) to (II-f)described above) is 10 to 40,000. If each segment in the block polymerhaving a polyvinyl ether structure is composed of two or more types ofmonomers, each segment may be a random polymer, gradient polymer orgraft polymer.

Other components of the present invention will be described below.

The solvent in the composition of the present invention is preferablywater or an aqueous solvent.

[Water]

Water contained in the composition of the present invention ispreferably ion exchanged water free from metal ions and the like, purewater or ultrapure water.

[Aqueous Solvent]

For the aqueous solvent, polyhydric alcohols such as ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol, propyleneglycol, polypropylene glycol and glycerin, polyhydric alcohol etherssuch as ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, diethylene glycol monoethylether and diethylene glycol monobutyl ether, nitrogen-containingsolvents such as N-methyl-2-pyrolidone, substituted pyrolidone andtriethanolamine, and the like may be used. For the purpose ofaccelerating drying on the recording medium, monohydric alcohol such asmethanol, ethanol and isopropyl alcohol may be used.

In the present invention, the content of water and aqueous solventdescribed above is 20 to 95 wt % based on the total weight of thecomposition. It is more preferably 30 to 90 wt %.

[Coloring Material]

The coloring material useful in the present invention may be pigment ordye depending on applications of the composition of the presentinvention. The coloring material that is used in the composition of thepresent invention is preferably 0.1 to 50 wt % based on the weight ofthe composition.

Specific examples of the pigment and dye for use in the composition ofthe present invention will now be described. The pigment may be eitheran organic pigment or inorganic pigment and for the pigment that is usedin ink, a black pigment and pigments of primary three colors, cyan,magenta and yellow, are preferably used. Pigments of other colors,colorless or light-colored pigments, metalescent pigments and the likemay be also used. Pigments newly synthesized for the present inventionmay also be used.

Commercially available black, cyan, magenta and yellow pigments will bedescribed with examples below.

Examples of black pigments include, but not limited to, Raven 1060,Raven 1080, Raven 1170, Raven 1200, Raven 1250, Raven 1255, Raven 1500,Raven 2000, Raven 3500, Raven 5250, Raven 5750, Raven 7000, Raven 5000ULTRA II, Raven 1190 ULTRA II (all of the above, from Columbian CarbonCompany), Black Pearls L, MOGUL-L, Regal 400R, Regal 660R, Regal 330R,Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1300,Monarch 1400 (all of the above, from Cabot Corporation), Color BlackFW1, Color Black FW2, Color Black FW200, Color Black 18, Color BlackS160, Color Black S170, Special Black 4, Special Black 4A, Special Black6, Printex 35, Printex U, Printex 140U, Printex V, Printex 140V (all ofthe above, from Degussa AG), No. 25, No. 33, No. 40, No. 47, No. 52, No.900, No. 2300, MCF-88, MA600, MA7, MA8, and MA100 (all of the above,from Mitsubishi Chemical Corporation).

Examples of cyan pigments include, but not limited to, C. I. PigmentBlue-1, C. I. Pigment Blue-2, C. I. Pigment Blue-3, C. I. PigmentBlue-15, C. I. Pigment Blue-15:2, C. I. Pigment Blue-15:3, C. I. PigmentBlue-15:4, C. I. Pigment Blue-16, C. I. Pigment Blue-22, and C. I.Pigment Blue-60.

Examples of magenta pigments include, but not limited to, C. I. PigmentRed-5, C. I. Pigment Red-7,

-   C. I. Pigment Red-12, C. I. Pigment Red-48, C. I. Pigment    Red-48:1, C. I. Pigment Red-57, C. I. Pigment Red-112, C. I. Pigment    Red-122, C. I. Pigment Red-123,-   C. I. Pigment Red-146, C. I. Pigment Red-168, C. I. Pigment    Red-184, C. I. Pigment Red-202, and C. I. Pigment Red-207.

Examples of yellow pigments include, but not limited to, C. I. PigmentYellow-12, C. I. Pigment Yellow-13, C. I. Pigment Yellow-14, C. I.Pigment Yellow-16, C. I. Pigment Yellow-17, C. I. Pigment Yellow-74, C.I. Pigment Yellow-83, C. I. Pigment Yellow-93, C. I. Pigment Yellow-95,C. I. Pigment Yellow-97, C. I. Pigment Yellow-98, C. I. PigmentYellow-114, C. I. Pigment Yellow-128, C. I. Pigment Yellow-129, C. I.Pigment Yellow-151, and C. I. Pigment Yellow-154.

In the composition of the present invention, pigments self-dispersing inwater (self-dispersing pigment) may also be used. Self dispersingpigments include those utilizing steric hindrance of a polymer adsorbedon the surface of the pigment and those utilizing electrostaticrepulsion, and commercially available such pigments include CAB-0-JET200and CAB-0-JET300 (manufactured by Cabot Co., Ltd.) and Microjet BlackCW-1 (manufactured by Orient Chemical Co., Ltd.).

The pigment content in the composition of the present invention ispreferably 0.1 to 50 wt % based on the weight of the composition. If thepigment content is less than 0.1 wt %, a sufficient image density cannotbe obtained, and if the pigment content is greater than 50 wt %,fixation of the image may be deteriorated. More preferably, the pigmentcontent is in the range of 0.5 wt % to 30 wt %.

Dyes that can be used in the composition of the present invention may beknown dyes including water soluble dyes such as a direct dye, acid dye,basic dye or reactive dye or food dyes, or insoluble dyes such as adisperse dye. Oil-soluble dyes may also be suitably used.

Examples of oil-soluble dyes include C. I. Solvent Blue-33, -38, -42,-45, -53, -65, -67, -70, -104, -114, -115, and -135; C. I. SolventRed-25, -31, -86, -92, -97, -118, -132, -160, -186, -187, and -219; andC. I. Solvent Yellow-1, -49, -62, -74, -79, -82, -83, -89, -90, -120,-121, -151, -153, and -154.

Examples of water-soluble dyes include direct dyes such as C. I. DirectBlack-17, -19, -22, -32, -38, -51, -62, -71, -108, -146, and -154;

-   C. I. Direct Yellow-12, -24, -26, -44, -86, -87, -98, -100, -130,    and -142;-   C. I. Direct Red-1, -4, -13, -17, -23, -28, -31, -62, -79, -81, -83,    -89, -227, -240, -242, and -243;-   C. I. Direct Blue-6, -22, -25, -71, -78, -86, -90, -106, and -199;-   C. I. Direct Orange-34, -39, -44, -46, and -60;-   C. I. Direct Violet-47 and -48;-   C. I. Direct Brown-109; and-   C. I. Direct Green-59; acid dyes such as C. I. Acid Black-2, -7,    -24, -26, -31, -52, -63, -112, -118, -168, -172, and -208;-   C. I. Acid Yellow-11, -17, -23, -25, -29, -42, -49, -61, and -71;-   C. I. Acid Red-1, -6, -8, -32, -37, -51, -52, -80, -85, -87, -92,    -94, -115, -180, -254, -256, -289, -315, and -317;-   C. I. Acid Blue-9, -22, -40, -59, -93, -102, -104, -113, -117, -120,    -167, -229, -234, and -254;-   C. I. Acid Orange-7 and -19; and-   C. I. Acid Violet-49; reactive dyes such as C. I. Reactive Black-1,    -5, -8, -13, -14, -23, -31, -34, and -39;-   C. I. Reactive Yellow-2, -3, -13, -15, -17, -18, -23, -24, -37, -42,    -57, -58, -64, -75, -76, -77, -79, -81, -84, -85, -87, -88, -91,    -92, -93, -95, -102, -111, -115, -116, -130, -131, -132, -133, -135,    -137, -139, -140, -142, -143, -144, -145, -146, -147, -148, -151,    -162, and -163;-   C. I. Reactive Red-3, -13, -16, -21, -22, -23, -24, -29, -31, -33,    -35, -45, -49, -55, -63, -85, -106, -109, -111, -112, -113, -114,    -118, -126, -128, -130, -131, -141, -151, -170, -171, -174, -176,    -177, -183, -184, -186, -187, -188, -190, -193, -194, -195, -196,    -200, -201, -202, -204, -206, -218, and -221;-   C. I. Reactive Blue-2, -3, -5, -8, -10, -13, -14, -15, -18, -19,    -21, -25, -27, -28, -38, -39, -40, -41, -49, -52, -63, -71, -72,    -74, -75, -77, -78, -79, -89, -100, -101, -104, -105, -119, -122,    -147, -158, -160, -162, -166, -169, -170, -171, -172, -173, -174,    -176, -179, -184, -190, -191, -194, -195, -198, -204, -211, -216,    and -217;-   C. I. Reactive Orange-5, -7, -11, -12, -13, -15, -16, -35, -45, -46,    -56, -62, -70, -72, -74, -82, -84, -87, -91, -92, -93, -95, -97, and    -99;-   C. I. Reactive Violet-1, -4, -5, -6, -22, -24, -33, -36, and -38;-   C. I. Reactive Green-5, -8, -12, -15, -19, and -23; and-   C. I. Reactive Brown-2, -7, -8, -9, -11, -16, -17, -18, -21, -24,    -26, -31, -32, and -33; and-   C. I. Basic Black-2;-   C. I. Basic Red-1, -2, -9, -12, -13, -14, and -27;-   C. I. Basic Blue-1, -3, -5, -7, -9, -24, -25, -26, -28, and -29;-   C. I. Basic Violet-7, -14, and -27; and-   C. I. Food Black-1 and -2.

Examples of the coloring materials described above are especiallypreferable for the composition of the present invention, but thecoloring material that is used in the composition of the presentinvention is not specifically limited to the coloring materialsdescribed above.

The content of the dye that is used in the composition of the presentinvention is preferably 0.1 to 50 wt % based on the weight of thecomposition. If the content of the dye is less than 0.1 wt %, asufficient image density cannot be obtained, and if the content isgreater than 50 wt %, fixation of the image may be deteriorated. Morepreferably, the content of the dye is in the range of 0.5 wt % to 30 wt%.

In the present invention, the pigment and the dye may be used inconjunction.

[Additives]

To the composition of the present invention, various kinds of additives,assistants and the like may be added as required.

One of additives of the composition is a dispersion stabilizer forstabilizing a pigment in a solvent. The composition of the presentinvention has a function of dispersing solid particles such as a pigmentwith a polymer having a polyvinyl ether structure, but if dispersion isin sufficient, other dispersion stabilizer may be added.

As other dispersion stabilizer, a resin having both hydrophilic andhydrophobic portions or a surfactant can be used.

Resins having both hydrophilic and hydrophobic portions include, forexample, copolymers of hydrophilic monomers and hydrophobic monomers.Hydrophilic monomers include acrylic acid, methacrylic acid, maleicacid, fumaric acid, the monocarboxylates described above, vinyl sulfonicacid, styrene sulfonic acid, vinyl alcohol, acrylamide andmethacryloxyethyl phosphate, and hydrophobic monomers include styrene,styrene derivatives such as α-methyl styrene, vinylcyclohexane, vinylnaphthalene derivatives, acrylates and methacrylates. For the copolymer,various copolymers such as random, block and graft copolymers may beused. Of course, hydrophilic and hydrophobic monomers are not limited tothose described above.

For the surfactant, anionic, nonionic, cationic and ampholyticsurfactants may be used.

Anionic surfactants include fatty acid esters, alkyl sulfates, alkylaryl sulfonates, alkyl diaryl ether disulfonates, dialkylsulfosuccinates, alkyl phosphates, formalin naphthalenesulfonatecondensates, polyoxyethylene alkyl phosphates and glycerol borate fattyacid esters.

Nonionic surfactants include polyoxyethylene alkyl ethers,polyoxyethylene oxypropylene block copolymers, sorbitan fatty acidesters, glycerin fatty acid esters, polyoxyethylene fatty acid esters,polyoxyethylene alkyl amines, fluorine surfactants and siliconsurfactants.

Cationic surfactants include alkyl amine salts, quaternary ammoniumsalts, alkyl pyridinium salts and alkyl imidazolium salts.

Ampholytic surfactants include alkyl betaines, alkyl amine oxides andphosphatidyl choline. Similarly, the surfactant is not limited to thosedescribed above.

A composition containing the additives described above is provided, forexample, as a composition different from the ink composition of thepresent invention, and it may be brought in contact, as required, withthe ink composition to give a stimulus. Specifically, in the case ofinkjet ink, for example, an ink tank containing an ink composition ofthe present invention and an ink tank containing a compositioncontaining additives are prepared, and the compositions are dischargedonto the same recording material separately and thus contacted with eachother. Alternatively, a composition containing additives is provided toa recording medium in advance, to which the ink composition of thepresent invention is applied for contact with each other.

To the composition of the present invention, an aqueous solvent may beadded as required. Particularly, if the composition is used in inkjetink, the aqueous solvent is used for prevention of drying andsolidification of the ink at a nozzle portion, and can be used alone orin mixture. For the aqueous solvent, those described above applydirectly. In the case of ink, the content of the solvent is 0.1 to 60 wt%, preferably 1 to 25 wt % based on the total weight of the ink.

Other additives for ink include, for example, a pH adjuster forstabilizing the ink in the feeding pipe in a recording apparatus, apenetration agent promoting penetration of the ink into the recordingmedium and accelerating apparent drying, anti-mold agent preventinggrowth of mold in the ink, a chelating agent blocking metal ions in theink and preventing precipitation of metals at the nozzle portion,precipitation of insoluble matters in the ink and the like, anantifoaming agent preventing foaming in during circulation and movementof a recording liquid or during production of the recording liquid, anantioxidant, a fungicide, a viscosity adjuster, a conducting agent, anultraviolet absorber, a water soluble dye, a disperse dye, anoil-soluble dye and the like.

Inkjet ink (aqueous dispersion ink), which is a preferred embodiment ofthe ink composition of the present invention, will be describedspecifically below.

[Method for Production of Inkjet Ink]

A method for production of the composition is characterized by a step ofencapsulating a coloring material in the block polymer where the blockpolymer is fully dissolved in a solvent, and then the solventenvironment is changed to cause inclusion of the coloring material inthe block polymer. More preferably, in the production step, the changein solvent environment is selected from change in pH, change intemperature and change in solvent hydrophilicity or a combination of twoor more of the changes. An example of the production method of inkjetink of the present invention will be described below.

To a block polymer having a vinyl ether structure in at least onesegment, a solvent that can fully dissolve the polymer is added. Thesolvent is selected depending on the solubility of the polymer. Forexample, in the case of (II-a), each segment is responsive to heat, sothat hydrophilicity and hydrophobicity can be controlled withtemperature, and the solvent may be water if the temperature is 20° C.or lower. When the polymer has a hydrophobic group as (II-e) being onlyone example, the solvent may be toluene, chloroform or methanol. Asolution of the block polymer is prepared in this way, then a coloringmaterial is added and dispersed using a dispersion apparatus, and thenthe solvent environment is changed to encapsulate the coloring material.An example of the composition-producing method where the change insolvent environment is selected from change in pH, temperature andhydrophilicity of the solvent or combination of two or more thereof isas follows: a block polymer II-a is dissolved in water at 20° C. orlower, a pigment is then added and dispersed, and the resultant solutionis heated to 25° C., whereby a segment comprised of 2-ethoxyethyl vinylether becomes hydrophobic and the block polymer becomes amphipathic, andmicelles are formed in water and the coloring material is includedtherein. In the case of (II-e), a pigment is added and dispersed in asolvent in which a block polymer has been dissolved, and water is addedto increase hydrophilicity of the solvent mixture, whereby the segmentcomprised of isobutyl vinyl ether causes phase separation to formmicelles in which the coloring material is included. If required, coarseparticles are then removed by centrifugal separation or the like. Ifnecessary, a water soluble solvent may added to the product followed bystirring, mixing and filtration.

Dispersion apparatuses include, for example, an ultrasonic homogenizer,a laboratory homogenizer, a colloid mill, a jet mill and a ball mill,and they may be used alone or in combination.

The composition can be produced in the same manner when aself-dispersing pigment or oil-soluble dye is used.

[Image Formation Method and Image Formation Apparatus]

The aqueous dispersion ink in the present invention can be used withvarious image formation apparatuses of various printing methods such asthe inkjet method and electrophotography, to form images by such anapparatus. If the composition is used as an inkjet ink, it can be usedin the following manner in the present invention. The ink agglomerateswith changes in solvent environment described below.

When the composition uses the block polymer (II-a), for example, animage can be formed using temperature as the change solvent environment.Due to the difference of the ink temperature in the tank and on therecording medium, the inkjet ink of the present invention cause phaseseparation resulting in rapid thickening or coagulation of insolublecomponents. Change in ink properties can improve blurring andfeathering, and excellent fixation can be achieved. The change in inkproperties is not limited to the above thickening or coagulation ofinsoluble components.

Similarly, an image can be formed changing the solvent environment byirradiation with electromagnetic wave, changing pH of the composition orchanging concentration. The change in temperature preferably covers thephase transition temperature of the composition. Regarding exposure toelectromagnetic wave, the wavelength of the electromagnetic wave ispreferably in the range of 100 to 800 nm. Regarding the change in pH, itis preferably in the range of pH 3 to pH 12. The change in thecomposition concentration preferably spans the concentration at whichthe composition causes phase transition.

For the method for giving a stimulus for changing the solventenvironment, various methods can be applied. One preferred method is amethod in which a composition giving a stimulus and the ink compositiondescribed above are mixed together or made to contact each other. Forexample, to cause a change in solvent environment by changing pH, acomposition having a corresponding pH can be mixed with the inkcomposition by using the ink jet method. As described in Japanese PatentApplication Laid-Open No. S64-63185, a composition giving a stimulus canbe applied to the entire surface of an area on which an image is formedby using an inkjet head, and as described in Japanese Patent ApplicationLaid-Open No. H8-216392, the amount of a composition giving a stimuluscan be controlled to form a better image.

The block polymer in the composition described above is preferablyamphipathic, and a preferable solvent is water. With such a composition,micelles of the block polymer are formed to disperse a pigmentexcellently. And since most of the block polymer molecules are notdissolved but dispersed in a micelle state, a relatively low viscositycan be achieved. For the block polymer in the present invention,polymers described above can be used, but a block polymer having apolyvinyl ether structure described above is preferable. In the presentinvention, the composition is brought into contact with a compositionthat gives a stimulus to the block polymer portion, whereby the micellesform a network structure together to thicken the ink for excellentfixation. Thus, the image formation method using the composition of thepresent invention can achieve excellent fixation.

When the inkjet ink of the present invention and the stimulatingcomposition are brought into contact, they may be applied as separatecompositions. For example, the inkjet composition and the stimulatingcomposition are put in separate packages, and contacted each other asrequired. In the case of inkjet ink, for example, an image can be formedby a method in which an ink tank containing the composition of thepresent invention and an ink tank containing the stimulating compositionare prepared independently, and the compositions are separatelydischarged onto the same recording medium and contacted each other toform an image. Alternatively, a stimulating composition is previouslyprovided to a recording medium by means such as coating or spraying, andthe ink composition of the present invention is then discharged onto therecording medium where the compositions contact with each other and forman image.

It is also preferable that a mechanism for giving a stimulus is providedin the recording medium in advance. In an example of such a method, a pHresponsive ink, specifically an acid responsive ink, is used to performrecording on a sheet of acid paper. In this case, the recording mediumhas a function of giving a stimulus to the stimulus-responsive ink ofthe present invention. This recording medium is included in the presentinvention. That is, the present invention relates to a recording mediumhaving a function of giving a stimulus. In the present invention, therecording medium may be of any known form. For example, the recordingmedium can be plain paper, heat sensitive paper or acid paper.

Inkjet printers using the inkjet ink of the present invention includevarious inkjet recording apparatuses such as a piezo inkjet system usinga piezoelectric element and a thermal inkjet system utilizing thermalenergy to make a bubble in the ink to perform recording.

For the apparatus of the present invention, in the case of inkjet ink,for example, the amount of ink discharged from a discharge port of adischarge head is preferably in the range of 0.1 to 100 picoliter.

The composition of the present invention may also be used in an indirectrecording apparatus using a recording system in which ink is printed onan intermediate transfer material, and then transferred to a recordingmedium such as paper. The composition may also be applied for anapparatus using an intermediate transfer material by a direct recordingsystem.

The ink composition of the present invention may be also used in animage formation method and apparatus system in the electrophotographicrecording system. An example image formation apparatus comprises aphotosensitive drum on which a latent image is formed, means for forminga latent image on the photosensitive drum such as a light exposuremeans, ink-applying means, a transfer mechanism and a recording medium.For formation of an image by this apparatus, a latent image is firstformed on the photosensitive drum, the composition of the presentinvention is applied to the latent image area or areas other than thelatent image, and the obtained image is transferred onto the recordingmedium by the transfer mechanism and fixed thereon.

The outline of an inkjet recording apparatus will be described belowwith reference to FIG. 1. However, FIG. 1 is only one example of theconfiguration and does not limit the invention of this application.

FIG. 1 is a block diagram showing the configuration of the inkjetrecording apparatus.

FIG. 1 shows recording onto a recording medium by moving a head. In FIG.1, an X direction driving motor 56 and a Y direction driving motor 58for driving a head 70 in X and Y directions is connected to a CPU 50controlling the overall operation of a production apparatus through an Xmotor driving circuit 52 and a Y motor driving circuit 54. The Xdirection driving motor 56 and the Y direction driving motor 58 aredriven through the X motor driving circuit 52 and the Y motor drivingcircuit 54 according to instructions by the CPU to determine a positionof the head 70 relative to the recording medium.

As shown in FIG. 1, in addition to the X direction driving motor 56 andthe Y direction driving motor 58, a head driving circuit 60 is connectedto the head 70, the CPU 50 controls the head driving circuit 60, anddrives the head 70, i.e. discharges inkjet ink, and so on. An X encoder62 and a Y encoder 64 for detecting the position of the head areconnected to the CPU 50, and information of the position of the head 70is input to the CPU 50. A control program is input to a program memory66. Based on this control program and information of the positions ofthe X encoder 62 and the Y encoder 64, the CPU 50 moves the head 70, andplaces the head to a desired position on a recording medium to dischargeinkjet ink. In this way, a desired image is formed on the recordingmedium. In the case of an image recording apparatus capable of loading aplurality of inkjet inks, a desired image can be formed on the recordingmedium by performing the above operation for each inkjet inkpredetermined times.

After inkjet ink is discharged, the head 70 can be moved to a positionat which removal means (not shown) for removing excessive ink depositedon the head is disposed, and cleaned by wiping or the like. For thespecific method of cleaning, a conventional method can be used directly.

When image formation is completed, the recording medium on which animage has been formed is replaced by a new recording medium with amechanism for conveyance of recording media (not shown).

In the present invention, the embodiment described above can be modifiedor altered without departing from the spirit of the invention. Forexample, an example in which the head 70 is moved along X and Y axes hasbeen described above, but a configuration is also possible in which thehead 70 is moved only along the X axis (or Y axis), the recording mediumis moved along the Y axis (or X axis), and an image is formed with theformer and the latter interlocked with each other.

In the present invention, means (e.g. electrothermal converter, laserlight, etc.) for generating heat energy as an energy source used fordischarging inkjet ink is provided, and a head discharging inkjet inkwith the heat energy brings about an excellent effect. According to sucha system, fineness of image formation can be enhanced. By using theinkjet ink of the present invention, further excellent images can beformed.

For the typical configuration and principle of the apparatus comprisingthe means for generating heat energy, basic principles disclosed in U.S.Pat. Nos. 4,723,129 and 4,740,796 specifications are preferably used.This system is applicable to both so called the on-demand type and thecontinuous type, but the on-demand type is especially effective becauseat least one drive signal matching discharge information and giving arapid increase in temperature exceeding nuclear boiling of a liquid isapplied to an electrothermal converter retaining the liquid and placedin correspondence with a channel, whereby the electrothermal converteris caused to generate heat energy, and film boiling is created on theheated surface of the head, so that a bubble is formed in the liquidcorresponding to the drive signal on a one-to-one basis. The liquid isdischarged through a discharge opening by the growth and shrinkage of abubble to form at least one droplet. This drive signal more preferablyhas a pulse shape because bubbles grow or shrink appropriately in aninstant, and therefore discharge of a liquid with excellent responsivitycan be achieved. For the drive signal having a pulse shape, thosedescribed in U.S. Pat. Nos. 4,463,359 and 4,345,262 specifications aresuitable. If conditions described in U.S. Pat. No. 4,313,124specification for an invention relating to a temperature-rise rate ofthe thermal action surface are employed, further excellent discharge canbe performed.

For the configuration of the head, the present invention includes aconfiguration described in U.S. Pat. Nos. 4,558,333 and 4,459,600disclosing a configuration in which a thermal action portion is placedin a curved area, in addition to the configuration of a combination of adischarge port, a liquid channel and an electrothermal converter (linearliquid channel or orthogonal liquid channel) as disclosed in thespecifications described above. In addition, the present invention iseffective even with a configuration based on Japanese Patent ApplicationLaid-Open No. 59-123670 disclosing a configuration in which for aplurality of electrothermal converters, a common slit is a dischargeportion of the electrothermal converters or Japanese Patent ApplicationLaid-Open No. 59-138461 in which a hole absorbing pressure waves of heatenergy is brought into correspondence with the discharge portion. Thatis, according to the present invention, inkjet ink can be dischargedreliably and efficiently irrespective of the form of the head.

Further, the present invention can effectively applied to a full linetype head having a length matching the largest width of the recordingmedium in the image formation apparatus of the present invention. Thehead may have either a configuration in which a plurality of heads arecombined to meet the length or configuration as one head integrallyformed.

In addition, the present invention is effective even if among serialtypes, a head fixed on an apparatus main body, or a replaceable chiptype head which is mounted on the apparatus main body so that electricalconnection can be established with the apparatus main body and ink canbe supplied from the apparatus main body is used.

Further, the apparatus of the present invention may comprise dropletremoving means. If the means is added, a further excellent dischargeeffect can be realized.

As a configuration of the apparatus of the present invention, additionof preliminary auxiliary means is preferable because the effect of thepresent invention can be still further stabilized. Specific examples ofthe means may include capping means for the head, pressure or suctionmeans, preliminary heating means for heating using an electrothermalconverter or other heating element or a combination thereof, andpreliminary discharge means for performing discharge other thandischarge of ink.

The apparatus that is the most effective for the present invention is anapparatus carrying out the film boiling method described above.

EXAMPLES

The present invention will be described in detail below with Examples,but the present invention is not limited to the Examples. In thefollowing Examples, a method for synthesizing a block polymer of thepresent invention is described as well as ink compositions dispersing anoil-soluble dye therein as examples of aqueous dispersions. In theExamples of synthesis of polymers and dye-dispersion ink, only severalspecific examples are described, but the present invention is notlimited to these examples.

Example 1

<Synthesis of Block Polymer>

Synthesis of a block polymer having a terminal carboxylic acid made of2-ethoxyethyl vinyl ether (EOVE), 2-methoxyethyl vinyl ether (MOVE) andHO(CH₂)₅COOH

Poly[EOVE(2-ethoxyethyl vinyl ether)-b-MOVE(methoxymethyl vinylether)]—O—(CH₂)₅COOH (b is a symbol indicating being block polymer) wassynthesized according to the following procedure.

A glass container provided with a three-way stopcock was flashed withnitrogen, and the glass container was then heated at 250° C. under anatmosphere of nitrogen gas to remove adsorbed water. When the systemreached the room temperature, 12 mmol of EOVE, 16 mmol of ethyl acetate,0.1 mmol of 1-isobutoxyethyl acetate and 11 ml of toluene were added,and the reaction system was cooled. When the system temperature reached0° C., 0.2 mmol of ethyl aluminum sesquichloride (equimolar mixture ofdiethyl aluminum chloride and ethyl aluminum dichloride) was added, andpolymerization was started. The molecular weight was monitored with timeby gel permeation column chromatography (GPC), and completion ofpolymerization of A component (EOVE) was confirmed.

Then, 12 mmol of B component (MOVE) was added, and polymerization wasperformed. Completion of polymerization of B component was confirmed byGPC, and 30 mmol of HO(CH₂)₅COOEt was then added to stop thepolymerization reaction. The reaction mixture solution was diluted withdichloromethane, and washed with 0.6 M hydrochloric acid three times,and then distilled with water three times. The resultant organic phasewas concentrated to solidify on an evaporator to obtain a block polymerof poly[EOVE-b-MOVE] —O(CH₂)₅COOEt.

The synthesized compound was identified by GPC and NMR. The end portionwas identified by confirming existence of a terminus in the spectrum ofhigh molecular weight materials by the NMR DOSY method. Mn was 2.1×10⁴,and Mw/Mn was 1.4. Mn represents a number average molecular weight, andMw represents a weight average molecular weight.

The ester portion at the end of the obtained poly[EOVE-b-MOVE]—O(CH₂)₅COOEt was hydrolyzed and identified by NMR to confirm thatpoly[EOVE-b-MOVE] —O(CH₂)₅COOH was obtained.

26 parts by weight of the thus obtained block polymer having acarboxylic acid terminus were stirred at 0° C. for 3 days together with200 parts by weight of an aqueous sodium hydroxide solution of pH 11 toprepare a solution of sodium carboxylate polymer where the polymer wasfully dissolved. The polymer was extracted with methylene chloride.After drying, the solvent was distilled away to isolate the polymer.

Then, 97 parts by weight of ion exchanged water were added to 4 parts byweight of the polymer, and the block polymer was dissolved at 0° C.using a homogenizer.

Then, 30 parts by weight of yellow oil-soluble dye (trade name: Yellow3150 manufactured by Orient Chemical Co., Ltd.) were dissolved in 70parts by weight of toluene. 20 parts by weight of the coloring materialsolution were added to 65 parts by weight of the block polymer aqueoussolution, and dispersed/mixed using a homogenizer at 0° C. The resultantmixture was heated to 25° C. to form micelles composed of the blockpolymer encapsulating the liquid coloring material. Finally, 10 parts byweight of diethylene glycol and 5 parts by weight of 2-pyrolidone wereadded, and mixed using a homogenizer. Then coarse particles werefiltered away to prepare an ink composition of the present invention.The structure including the liquid coloring material was observed usingelectron microscope observation.

When the ink composition was contacted with a 5 wt % aqueouspolymethacrylic acid solution adjusted to pH 2, yellow agglomerates wereformed to confirm that the ink composition was responsive to a stimulus.

Example 2

A 5 wt % aqueous polymethacrylic acid solution adjusted to be pH 2 asused in Example 1 was sprayed onto a sheet of plain paper. Then printingwas carried out by spraying the ink composition produced in Example 1onto the paper.

One minute after the spraying of the ink composition, a blank plainpaper was pressed against the printed area under a load of 4.9×10⁴ N/m²to evaluate the fixation strength on the basis whether or not the blankplain paper was smeared with the ink. Ink smear on the blank plain paperwas not observed. The same test was conducted five times, and the sameresult was obtained for each test.

Comparative Example 1

6 parts by weight of yellow oil-soluble dye (trade name: Yellow 3150manufactured by Orient Chemical Co., Ltd.) were dissolved in 94 parts byweight of toluene, and printing and evaluation of fixation strength werecarried out in the same manner as in Example 2. The ink attached ontothe blank plain paper was observed.

Example 3

<Synthesis of Block Polymer>

Synthesis of diblock polymer composed of isobutyl vinyl ether andCH₂═CHOCH₂CH₂OPhPh (IBVE-r-VEEtPhPH: A block) and 2-methoxyethyl vinylether (MOVE: B block)

A glass container provided with a three-way stopcock was flashed withnitrogen gas, and then heated at 250° C. under a nitrogen atmosphere toremove adsorbed water. The system was returned to room temperature, towhich 6 mmol of IBVE, 6 mmol of VEEtPhPh, 16 mmol of ethyl acetate, 0.1mmol of 1-isobutoxyethyl acetate and 11 ml of toluene were added. Thenthe reaction system was cooled to 0° C., 0.2 mmol of ethyl aluminumsesquichloride (equimolar mixture of diethyl aluminum chloride and ethylaluminum dichloride) was added thereto to start polymerization. Themolecular weight was monitored with time by gel permeationchromatography (GPC), and completion of polymerization of A block wasconfirmed.

Then, 24 mmol of MOVE for B block was added and polymerization wascontinued. Completion of polymerization of B block was confirmed bymonitoring using GPC, and then the polymerization reaction was stoppedby adding 0.3% by mass of an aqueous ammonia/methanol solution to thesystem. The reaction mixture solution was diluted with dichloromethane,and washed with 0.6 M hydrochloric acid three times, and then withdistilled water three times. The resultant organic phase wasconcentrated to dryness on an evaporator. The resultant material wasdried under vacuum, and then repeatedly dialyzed against methanol usinga semipermeable cellulose membrane to remove monomers and obtain adiblock polymer as a desired product. The compound was identified by NMRand GPC. Mn was 32500, and Mw/Mn was 1.24. The polymerization ratio wasA:B=100:200. The polymerization ratio of two types of monomers in Ablock was 1:1.

Example 4

15 parts by mass of the AB type diblock polymer obtained in Example 3were, dissolved in 150 parts by mass of dimethyl formamide, and theresultant solution was gradually converted into a water phase using 400parts by mass of distilled water to obtain an aqueous polymerdispersion.

Example 5

1 ml of the aqueous polymer dispersion obtained in Example 4, 4 ml of a0.1 mol/l aqueous NaOH solution and 75 ml of distilled water were mixed,to which a 0.1 mol/l aqueous HCl solution was gradually added measuringpH and DLS (dynamic light scattering). The results are shown below.

Amount of 0.1 N Particle size HCl aq added (ml) pH (nm) 0 11.3 102 2.010.6 99 3.5 8.9 89 4.0 6.8 75 4.5 3.3 84 6.0 2.8 91

As described above, the nonionic hydrophilic polymer extended its chainin both acidic and alkaline solutions with increase in micelle diameter.

Example 6

15 parts by mass of the AB type diblock polymer obtained in Example 3and 7 parts by mass of oil blue N (C.I. Solvent Blue-14 manufactured byAldrich Co., Ltd.) were co-dissolved in 150 parts by mass of dimethylformamide, and the resultant solution was gradually converted into awater phase using 400 parts by mass of distilled water. Thus an inkcomposition was obtained. Oil blue N was not separately precipitatedeven after the ink composition was left standing for 10 days.

Comparative Example 2

2 parts by mass of a black self-dispersing pigment (trade name:CAB-0-JET300 manufactured by Cabot Co., Ltd.), 0.5 parts by mass of asurfactant (Nonion E-230 manufactured by NOF Corporation), 5 parts bymass of ethylene glycol and 92.5 parts by mass of ion exchanged waterwere mixed to prepare an ink composition. The ink composition was filledin a print head of an inkjet printer (trade name: BJF800 manufactured byCanon Inc.) to perform solid printing. One minute after printing, theprinted area was strongly rubbed with a line marker five times. Blacktailing was observed after the first run.

Example 7

An aqueous hydrochloric acid solution of pH 3 was sprayed onto a sheetof plain paper to produce a recording medium. The ink compositionobtained in Example 6 was filled in a print head of an inkjet printer(trade name: BJF800 manufactured by Canon Inc.) to perform solidprinting on the recording medium. One minute after printing, the printedarea was strongly rubbed with a line marker five times but no bluetailing was observed. Thus fixation of the ink composition was verygood.

Comparative Example 3

The ink composition obtained in Example 6 was filled in a print head ofan inkjet printer (trade name: BJF800 manufactured by Canon Inc.) toperform solid printing on a sheet of plain paper. One minute afterprinting, the printed area was strongly rubbed with a line marker fivetimes. Blue tailing was observed after the fourth run.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, a compositionexcellent in fixation, particularly an inkjet ink, can be provided. Thecomposition comprises at least a block polymer encapsulating a materialof a predetermined function and a solvent, and is characterized in thata property of the block polymer in the composition is changed inresponse to a stimulus, whereby the block polymer encapsulating thematerial agglomerate together.

The present invention can provide print images excellent in fixationaccording to an image formation method using the composition and animage formation apparatus that is used in the method.

1. An image formation method wherein an image is formed through a process that a composition comprising a block polymer encapsulating a functional material of a predetermined function and a solvent is applied to a medium, and a property of the block polymer is changed in response to a received stimulus, whereby the block polymer encapsulating the functional material agglomerates together, wherein the stimulus is a change in pH, and the size of particles in the composition comprising the block polymer encapsulating the functional material is increased by the change in pH, whereby an image is formed on a medium. 